title: Possible role of the adhesin ace and collagen adherence in conveying resistance to disinfectants on Enterococcus faecalis.
abstract: BACKGROUND
  This study aimed to evaluate whether the presence of the ace gene and Ace-mediated binding to collagen confers on Enterococcus faecalis resistance against common endodontic disinfectants.
  
  
  METHODS
  Isogenic strains of E. faecalis: OG1RF (wild-type) and TX5256 (ace insertion mutant of OG1RF) were grown in brain-heart infusion broth at 46 degrees C overnight. Standardized bacterial suspensions were pretreated for 1 h either with acid-soluble collagen or acidified phosphate-buffered saline (ac-PBS). Bacteria were challenged with chlorhexidine digluconate (CHX), iodine potassium-iodide (IKI), sodium hypochlorite (NaOCl), and calcium hydroxide [Ca(OH)(2)]. Samples were removed at 1, 3, and 6 h, and cultured on Todd-Hewitt agar plates. Colonies were counted, the absolute values were log transformed, and the data were statistically analyzed using Fisher's least significant differences test and t-test.
  
  
  RESULTS
  OG1RF was more resistant than TX5256 to IKI, NaOCl, and Ca(OH)(2) (P < 0.05). Collagen-exposed OG1RF was more resistant than the ac-PBS-pretreated OG1RF against CHX at 3 h and against IKI at 1 h (P < 0.05); no significant difference was found against NaOCl. As expected, the ace mutant strain, TX5256, pretreated with collagen or ac-PBS did not differ significantly in viability when challenged with CHX, IKI, and NaOCl. An unexpected result was found for Ca(OH)(2): collagen-pretreated OG1RF and TX5256 were both more susceptible than ac-PBS-pretreated OG1RF and TX5256, respectively (P < 0.05).
  
  
  CONCLUSIONS
  The presence of the ace gene confers resistance against IKI, NaOCl, and Ca(OH)(2) on E. faecalis. Exposure to collagen makes the wild-type bacterium more resistant against CHX and IKI; however, exposure to collagen apparently decreases resistance to Ca(OH)(2).
authors.affiliation: Department of Endodontics and Conservative Treatment, Faculty of Dentistry, Gazi University, Ankara, Turkey. guvenk@gazi.edu.tr
authors.forename: G
authors.initials: G
authors.lastname: Kayaoglu
authors.forename: H
authors.initials: H
authors.lastname: Erten
authors.forename: D
authors.initials: D
authors.lastname: Ørstavik
mesh_terms: D000891:Anti-Infective Agents, Local / Q000494:pharmacology; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002126:Calcium Hydroxide / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002710:Chlorhexidine / Q000031:analogs & derivatives / Q000494:pharmacology; D003094:Collagen / Q000378:metabolism*; D015169:Colony Count, Microbial; D004202:Disinfectants / Q000494:pharmacology*; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017613:Iodine Compounds / Q000494:pharmacology; D012388:Root Canal Irrigants / Q000494:pharmacology; D012973:Sodium Hypochlorite / Q000494:pharmacology
chemical_list: C121675:Ace protein, Enterococcus; D000891:Anti-Infective Agents, Local; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004202:Disinfectants; D017613:Iodine Compounds; D012388:Root Canal Irrigants; C439385:iodine potassium iodide; D003094:Collagen; D012973:Sodium Hypochlorite; C010882:chlorhexidine gluconate; D002126:Calcium Hydroxide; D002710:Chlorhexidine